In species with simultaneous polyandry, male-biased operational sex ratio is expected to increase the risk of sperm competition and thus sperm traits affecting siring success can differ among populations. Here, we test the hypothesis that high male–female ratios will enhance sperm competitiveness of Rana temporaria males. In this species, local populations can show either prolonged or explosive breeding. In a context of sperm competition and in controlled laboratory conditions, prolonged-breeding males sired a higher proportion of eggs than explosive-breeding males, regardless of female origin. This study demonstrates intrapopulation variation in siring success under a situation of sperm competition, consistent with the prolonged-explosive dichotomy of breeding strategies.